The biomolecular composition of human tissues, represented by a multitude of lipids, proteins, nucleic acids, and other miscellaneous molecules, is a sensitive indicator of local pathologies, such as cancer, allergies, and eczema, as well as several systemic diseases, such as cardiovascular disease, Alzheimer's disease, and diabetes. In addition, tissue molecular composition also holds critical information about the body's exposure to exogenous chemical and biological entities. However, this information is not currently used in diagnostic methods due to a lack of patient-friendly and standardized methods for routine sample collection from tissues. Instead, clinical diagnosis is invariably performed by visual observation and histopathological analysis of tissue biopsies, which are highly limited due to their qualitative nature, leading to increased misdiagnosis and inappropriate use. In addition to being invasive, current methods also fall short in explaining a complete molecular genesis of diseases, and fail to distinguish between diseases.
Prior approaches using physical and chemical methods for assessing tissue fluid have focused chiefly on extracting a few low molecular weight molecules that are freely present in the interstitial fluid, such as calcium and glucose. Use of tape stripping for physically harvesting superficially-lying tissue constituents with an adhesive tape has been reported; however this technique has been shown to be limited by inefficacy, lack of a standardized protocol, and high heterogeneity in tissue sampling.